Service

The hot-finished tubes are produced by means of the Erhardt push bench process. The input material for the process is highgrade square billets that have been divided up into blocks by billet shears or a carbide-tipped saw. The blocks are preheated in a rotary plate furnace, and in the following rotary hearth furnace reach the optimal working temperature for the given grade of steel. After removal from the furnace, the blocks are sized and descaled, then formed to fill out the shell in a punching press. The shell is then approximately 80% bloomed in a downstream stop bench.

Rolling out the tube blanks is performed at the same heat in a push bench with an impact force of 138 t over a 15.5 m long mandrel bar in up to 16 roll passes. The resulting tube blank is slightly expanded between rolls in a detaching mill and the mandrel bar is then withdrawn in a two-roll mandrel extractor. The base and back end of the tube blank is then sawed off on following hot saws. The tube blanks are then heated in a walking-beam furnace, aided by inductive heating, to the rolling temperature which is optimal for the given steel quality.

In a 6-stand sizing mill and connected 28-stand stretch reducing mill, the tube blanks are rolled out using state-of-theart rolling technology to finished tube dimensions of 21.3 mm up to 139.7 mm outer diameter. The entire rolling process is computer-controlled and computermonitored so as to ensure the highest possible process precision and product quality. Following the hot-finishing stage of the tube are dressing and straightening lines that straighten all of the tubes, check them for surface defects and leak-tightness by non-destructive means, divide them into supplied lengths and package them as required for a particular order.

Both smooth-end “black” tubes and threaded tubes then move to the shipping storage area which are then threaded by a modern thread-cutting machine and/or provided with a socket. All tubes then are sent directly to the shipping storage area. In addition the tubes can be threaded by a modern thread-cutting machine and / or provided with a socket. Rohrwerk Maxhütte is Europe’s only tube manufacturer which is able to offer tubes that are galvanized in its own facility.